I've got a 2005 Escalade with 50K miles. I bought it about 2 months ago and everything worked fine. We took an extended trip this week towing our popup camper (tongue weight of about 250 lbs) and had a bad time with it. Whenever we started the car (with the camper hooked up) the compressor started like it should and pumped up the shocks like it was supposed to do. Over the course of about 1/2 hour the back end would be sagged down. I could stop the car and nothing would happen. If I stopped the engine and then restarted it would pump up the back end. If I had to guess as to the reason I would say that the controller is messed up. It acts as if it will not re-pump once I start the actual towing.

Fortunately I have an extended warranty. So I can take it in for service. My fear is that the dealer will say there is a problem with the shocks and they need to be replaced. I assume that they will consider this a consumable, normal maintenance item and not replace them at no charge.

Is there anything people can tell me about the operation of the system and if I am experiencing a problem? Any help would be appreciated.

Ed
www.edbianchina.com - Astrophotography

sk7

08-17-09, 09:50 AM

You can have a look at the thread about the compressor relay location, I posted some diagnostic tests that can be done to troubleshoot air ride system. Only issue imo that can arise with the shocks is a leak, which you can easily check yourself with a spray bottle with water and a bit of dishwashing soap added to find leaks. Do you get an error code for the air ride system? Mine doesnt work on my 02. Compressor works fine when I bypass the relay (I added a switch), but won't work automatically, and I get no error codes. Shocks are brand new.

I agree with you if you can understand how the system works you stand less of a chance of getting some BS from the dealership. When I had my truck inspected for salvage rebuilt, they told me I had to replace the rear shocks, since they were shot (the boot was torn and hanging down...). Tech advisor tells me ''Yeah those shocks need to be replaced, we can hear the compressor running and they leak bad''. Oh yeah? How did you manage to get that compresor to run, I've had the truck sitting in my garage for 6 months and have yet to hear it run??? :hmm:

luxurylife33

08-17-09, 12:50 PM

im starting to think its my rear shocks..... im going to do that spray bottle trick after i manually pump some air into them

sk7

08-17-09, 01:31 PM

I was just reviewing the diagnostic info I posted in the other thread (still at work today), and I think I will check the pressure sensor voltage first. Since I'm getting no trouble codes, it would make sense that the sensor(s) failed in the upper range (close to 5 volts at the SCM), then the module thinks suspension is fully charged and doesnt do anything.

A leak in the system will set a code if the compressor runs uninterupted for 5 minutes without any change in the rear level signal inputs. So a small leak can't be that bad. I wonder how long it takes for the SCM to react to a drop in pressure - rear level signal, and activates the compressor?

If that (air pressure sensor) checks out, I'll look at the exhaust solenoid. Still dunno exactly what its supposed to do but I'll try to figure it out. Crappy day coming up tomorrow (off work), so ECBM off, test ABS motor, then SCM. Buzy day ahead!

luxurylife33

08-17-09, 01:51 PM

Yea I seen in the other thread that the compressor would throw a code after 5 mins of no change.... i never had the compressor run for more than 20-30 seconds though. So maybe its the sensors .....grrrrrrrrrrrrrrrrrrrrrrr.... i will have to take a multimeter and also check the sensors...... im guessing the truck must be running and all 4 wheels on the ground? how am I going to get access to the sensor if the car must be on the ground?

sk7

08-17-09, 02:21 PM

All the sensors input are at the SCM. I'm gonna hookup my multi-test device on one of the back sensors, take a reading, then activate the compressor via the blue wire (which is also at the SCM module) and see if it changes. Since my shocks were in pretty bad shape, maybe the rear sensors were bypassed to prevent the compressor from running and throwing a code. Would be nice.... I think the SCM is easily accessible on the EXT? Got to remove the rear trim piece on the passenger side on mine. I'm gonna leave it off for the time being, I also got URPA issues...

I think the level sensors (rheostat device with a lever arm) are used as a pressure signal for the back. Not sure about that one. Will be a bit clearer tomorrow with a few cold ones!

luxurylife33

08-17-09, 02:46 PM

The URPA problems are easily fixed.... there was a thread with direction on how to use a jumper to troubleshoot which sensors were bad... my test resulted in one bad sensor, replaced it and works 100% now.

The SCM in the EXT is right under the rear seat, covered in some plastic covers which can be accessed in about 1 minute. If you could post the readout of the wires on the SCM, that would be great!

We should also move our convo back to the other thread to keep everything in one thread, although i think the title of this thread is more fitting than "relay location"

luxurylife33

08-17-09, 03:36 PM

i stayed home from work today (thank god i can make my own hours) .... beautiful day outside, gunna tear apart the rear and see whats going on with this suspension... if you could post the wiring diagram for the SCM that would be great.... interested to see the voltage coming from the sensors.....

sk7

08-17-09, 04:13 PM

I'll post that info tonight when I get home. I did the URPA diagnostic with the jumper, works great. I replaced one with a cheapo repro china made model (I was missing a sensor), it checks ok. I get one sensor defect. If I switch it with another one that is supposedly good, I still get that one defect + the other one I switched. I'll need another sensor for sure... If you wanna wait till tomorrow I can post what I'll find on my side and take it from there.

luxurylife33

08-17-09, 04:34 PM

cool.... i got 1 brand new sensor if your interested $58 shipped priority mail... its factory painted a beige color but can be painted one more time... bought it as a set of 4.... sold the other 2 to members on here

luxurylife33

08-17-09, 05:08 PM

Ok... according to your diagram in the other thread the sensors are both lightgreen/white wires at the SCM. One of those wires measured 2.78v and the other read 2.61v so I think that should be normal right? I think you said anything under 5 is normal? At what voltage does the SCM kick the compressor on?

EDIT:

DTC C0711
Circuit Description
The suspension control module uses a 5 volt analog air pressure sensor to determine the amount of air pressure in the Automatic Level Control (ALC ) system. The valid signal voltage range of the sensor is 0.15-4.85 volts. The sensor signal voltage will increase and decrease within the valid voltage range as system pressure increases and decreases.

So it seems my sensors are working properly .... tempted to by the $30 relay and see if that the problem....

sk7

08-17-09, 05:17 PM

Yeah I'll take that sensor! I paid over $100 for my el cheapo-repro. I'll pm you the info...

The lower the voltage the lower the pressure, fully charged rear suspension should be in the area of 4.8 volts. I didn't see info about the value at which the compressor kicks in. Would like to know that one for sure... As a test I unplugged one of the shocks (driver side was easier to do) cuz I wasnt sure if compressor was actually pumping. That would lower the truck, lower your voltage at the sensors, and with key on compressor should start.

luxurylife33

08-17-09, 05:23 PM

I jacked the rear end up to its normal height when the compressor is working and got 2.27v and 2.14v at the sensors..... would it be bad to put 4 volts to each sensor and see if it kicks on?

sk7

08-17-09, 05:30 PM

I would unplug one of the hose to depressurize the system, see what reading you get on those sensors, and compressor should kick on. Have a test light on that blue wire to see if it triggers some negative output to the relay.

luxurylife33

08-17-09, 06:05 PM

ZERO pressure in the system when I disconnected the hose! SHIT!

I think I accidentally discovered my problem..... I put a jack underneath the tow hitch to use as a stationary object to measure to see if the compressor was pumping air into the shocks. I manually pumped air into the system for about 45 seconds and gained a total of 2 1/2 inches from the jack to the tow hitch. At this point the compressor was working fine and pumping air into the struts. I took the jumper out of the relay, went towards the back and within 30 seconds the entire system dropped back down to the jack! So I have determined there is a major leak somewhere! Im going back out to do the soap/water trick on the shocks and will report my results! Thanks for the help thus far sk7!

luxurylife33

08-17-09, 06:22 PM

*fingers crossed* problem solved....

both shocks leaking like a mofo!

http://i161.photobucket.com/albums/t222/luxurylife33/bubbles.jpg

Good thing we stayed in this thread... The OP should try the bubble method! Those bubbles just started popping! .... any cheap places to buy the shocks?

luxurylife33

08-17-09, 07:29 PM

Went ahead with the Bilstein air shocks from Arnott. They come with a LIFETIME warranty, unlike the OEM's which were $100 more anyway. Arnott also offer a 90 day satisfaction guarantee or else they offer a full refund. The Bilsteins came out to $391 with 3 day ground shipping which isn't too bad. I will keep you guys updated once they are installed!

Glad to hear! I also wanted to go with those, but I was short on time, truck was at the inspection center waiting for new shocks so it could pass. I got the monroes for $440 canadian each, they sell for $420 US on fleabay (for both!). They look identical to the oem ones! And come with a lifetime warranty. I'll post my results tomorrow from my investigation.

luxurylife33

08-24-09, 10:18 PM

installed the bilsteins and still have the message.... took the ground off the battery for 10 mins to reset the computers and it still didn't get rid of the message...... whats next ? :(

sk7

08-25-09, 01:02 PM

Does the compressor come on every time the ignition is switched on? I know u suspected the relay to be defect, I would wire as a temporary test a regular 30/40A 12V relay there see if that solves the problem. I haven't worked on mine yet, waiting for the EBCM to come back from repairs and I still have knock sensor issues.

luxurylife33

08-25-09, 10:34 PM

napa has a stock relay for $18 .... no returns though since its an electric part .... im thinking the front shocks might be bad too.... are those shocks air or gas? i see a sensor plug for the front "electric shock" but dont see an air inlet .... is there a way to test if these are bad?

sk7

08-26-09, 07:50 PM

Auto leveling suspension only monitors the back shocks. I can fax you those troubleshooting GM sheets tomorrow, I'm working days. PM me your fax number if you want em.

luxurylife33

08-26-09, 08:07 PM

Auto leveling suspension only monitors the back shocks. I can fax you those troubleshooting GM sheets tomorrow, I'm working days. PM me your fax number if you want em.

Thanks! but i bought the DVD over the weekend so I should have it anyday, dont worry about it. So you think "service ride control" message has nothing to do with the front shocks?

sk7

08-26-09, 08:16 PM

Imo I don't think you need to worry about the fronts, they are not connected to the air compressor. Since your SCM is easily accessible, I would wire a light or siren or ? to the negative blue trigger for the relay, to alert you that the module is sending a command to the relay requesting activation of the compressor. If that works, then the relay is bad. If not there's an issue with the SCM... I get nothing from the SCM on mine. I'm starting to suspect the rear level sensors have been messed with, so the SCM always thinks the truck is level and doesnt require any air. The rear shocks were thrashed on it (boot was hanging off the shock!). It would make sense to wire a resistance value on the sensors to disable the system completely. As soon as I can get my EBCM installed, I'm gonna get to work on the air ride.

luxurylife33

08-29-09, 09:43 PM

Well apparently my left front shock is blown. Yesterday it started making loud noises consistent with a blown shock. Since they were most likley never changed and the car has 87k miles, I went ahead and ordered the pair of front shocks, OEM from Arnott. I'll install em when they come in and I'll take it from there. There is some sort of sensor that plugs into it, so it has send a message when its blown..... i assume...

sk7

08-29-09, 10:08 PM

From my understanding, the SCM can vary the voltage to the schocks and alter the damping according to road conditions (ie, variations in the up and down movement of the truck via the sensors on the 4 corners of the vehicule). The back sensors are also used for the auto leveling suspension (air assisted) to provide a reference as to the height of the rear. You are on the right track to getting this system full operational! There might be a way to test the front shocks by reading the resistance they have fully up or down in the service manual? Gotta look into that one...

oldworld

08-29-09, 10:21 PM

Hey LuxLife;
can you post the tab for the front shocks like you did for the rear shocks??
I'd like to have them both for future reference, as I am sure I will need both sets within the next year or so.
Thanks

luxurylife33

08-29-09, 10:43 PM

From my understanding, the SCM can vary the voltage to the schocks and alter the damping according to road conditions (ie, variations in the up and down movement of the truck via the sensors on the 4 corners of the vehicule). The back sensors are also used for the auto leveling suspension (air assisted) to provide a reference as to the height of the rear. You are on the right track to getting this system full operational! There might be a way to test the front shocks by reading the resistance they have fully up or down in the service manual? Gotta look into that one...

That would be great! Even if the fronts aren't the problem with the ride control message, I know at least one is blown and would like new shocks, since I plan on owning the truck a few more years.